Taper-tap



( OMO Z1 1 I v GRIBBBNI TAPER TAP.

No. 375,284. Patented Dec. 20, 1887.

xxx-m UNITED STATES PATENT OFFICE.

JOHN GRIBBEN, OF PITTSBURG, ASSIGNOR OF ONE-HALF TO FRANK H. CLARK, OFALLEGHENY COUNTY, PENNSYLVANIA.

TAPER-TAP.

SPECIFICATION forming part of Letters Patent No. 375,284, dated December20, 1887.

Application filed July 7, 1887. Serial No. 243,699. (No model.)

To aZZ whom it may concern:

Be it known that I, JOHN GRIBBEN, a citizen of the United States,residing at Pittsburg, in the county of Allegheny and State ofPennsylvania, have invented certain new and useful Improvements in Tapsfor Forming Taporing Screw-Threads in Sockets; and I do hereby declarethe following to be a full, clear, and exact description of theinvention, such as will enable others skilled in the art to which itpertains to make and use the same, reference being had to theaccompanying drawings, which form a part of this specification. I

My-invention relates to an improvement in taps for forming taperingvscrew-threads, the object being to provide a tap with two independentsets of cutting-blades, the first and stationary set to enter inadvance, in order to perform the heavy portion of the work, leaving thesecond or moving set only that portion of the work as is required tofinish the thread already formed to the required taper; and with thiscndin view myinvention consists in certain details of construction andcombination of parts, as will be fully described hereinafter.

In the accompanying drawings, Figure 1 is a sectional view taken throughthe center of the tap on the line :0 00. Fig. 2 is a rear end view ofthe same. Fig. 3 is a cross-section of my improved tap, taken on thelineyy. Fig. 4 is an outside elevation showing the relative position ofthe two sets of cutting-blades.

To put my invention into practice, I provide a cutter-head, a, ofsuitable size and form of construction,having a central circular openingextending through its entire length, in which is neatly fitted a fixedrod or shaft, 1), provided near one end with a double tapering portion,(1, corresponding to the desired taper of the socket. A portion, 0, ofthe rear of this cutter-head (t is in the form of a square, the objectof which is to afford a means for applying power to the same. At theforward end of this cutterehead a, I arrange in radial lines a suitablenumber of cutting-blades, f, which are capable of a slight movement inthe direction of their length, and limited to that movement by smallset-screws 9, project ing into grooves h, formed in the rear of eachblade f. These cutter-blades f are placed in radial slots formed in thehead a, and held in that position by neatly-fitting projections t",formed on a cap, j, which is securely bolted to the forward end of thecutter-head a. Between these cutter-bladesf, Iarrange another set, It,projecting some distance in advance of those first mentioned. This setof blades is are permanently secured in slots in the cutterhead a, andheld rigidly in that position by the cap j.

It will be seen by reference to Fig. 3 on the drawings that thecutting-edge of each blade, both stationary and movable, is in radialline with the cutter-head a. The object of this arrangement is to havethe edge doing the cutting slightly in advance of the heel or rear ofthe blades.

In operation the central shaft, 1), is fixed stationary and thecutter-head (4 moved back until the movable blades f, by means of thetapering portion (1 of the shaft Z1, are out to their full extent.Suitable power is applied to the cutter-head to slowly revolve the same.The stationaryblades k first entering the socket perform the heavycutting at the start, leaving the movable blades f to form the taper, byreason of the same moving along the tapering.portion d'of the fixedshaft b.

Any required taper may be given the thread in the socket by substitutingshafts b, having different tapers.

Having thus described my invention, what I claim, and desire to secureby Letters Patent, 1s-

1. In a tap for the purpose set forth, the cutter-head to, having aseries of radially-arranged cutting-blades, f, capable of a limitedmovement in the direction of their length, and an intervening set offixed or stationary blades, 76, operating in advance of those first mentioned, as and for the purpose described.

2. In a tap for forming tapering screwthreads in sockets, the movingcutting-blades f, secured in the cutter-head a by set-screws g, whichallow the same a short movement in the direction of their length, thefixed or stationary blades k, the central shaft, I), having a taperingportion, (2, formed thereon, and tense in advance of the moving blades,as and the capj, for holding the cutting-bladesf k in for the purposeset forth.

position. 7 T 3. In a tap for the purpose described, the JOHN GRIBBDI" 5fixed and moving cutting-blades arranged in "Witnesses:

the head a in radial lines and alternately with M. E. HARRISON, eachother, the fixed blades is being some dis- H. T. MORRIS.

